I. Field
The following description relates generally to wireless communications, and more particularly to providing uplink delay budget feedback in a wireless communication system.
II. Background
Wireless communication systems are widely deployed to provide various types of communication; for instance, voice and/or data can be provided via such wireless communication systems. A typical wireless communication system, or network, can provide multiple users access to one or more shared resources (e.g., bandwidth, transmit power, . . . ). For instance, a system can use a variety of multiple access techniques such as Frequency Division Multiplexing (FDM), Time Division Multiplexing (TDM), Code Division Multiplexing (CDM), Orthogonal Frequency Division Multiplexing (OFDM), and others.
Generally, wireless multiple-access communication systems can simultaneously support communication for multiple access terminals. Each access terminal can communicate with one or more base stations via transmissions on forward and reverse links. The forward link (or downlink) refers to the communication link from base stations to access terminals, and the reverse link (or uplink) refers to the communication link from access terminals to base stations. This communication link can be established via a single-in-single-out, multiple-in-single-out or a multiple-in-multiple-out (MIMO) system.
MIMO systems commonly employ multiple (NT) transmit antennas and multiple (NR) receive antennas for data transmission. A MIMO channel formed by the NT transmit and NR receive antennas can be decomposed into NS independent channels, which can be referred to as spatial channels, where NS≦{NT,NR}. Each of the NS independent channels corresponds to a dimension. Moreover, MIMO systems can provide improved performance (e.g., increased spectral efficiency, higher throughput and/or greater reliability) if the additional dimensionalities created by the multiple transmit and receive antennas are utilized.
MIMO systems can support various duplexing techniques to divide forward and reverse link communications over a common physical medium. For instance, frequency division duplex (FDD) systems can utilize disparate frequency regions for forward and reverse link communications. Further, in time division duplex (TDD) systems, forward and reverse link communications can employ a common frequency region so that the reciprocity principle allows estimation of the forward link channel from reverse link channel.
Wireless communication systems oftentimes employ one or more base stations that provide a coverage area. A typical base station can transmit multiple data streams for broadcast, multicast and/or unicast services, wherein a data stream may be a stream of data that can be of independent reception interest to an access terminal. An access terminal within the coverage area of such base station can be employed to receive one, more than one, or all the data streams carried by the composite stream. Likewise, an access terminal can transmit data to the base station or another access terminal.
In Long Term Evolution (LTE) based systems, a base station typically schedules uplink transmissions for an access terminal. Accordingly, the access terminal can be unable to send an uplink transmission unless scheduled by the base station. The base station can obtain knowledge of data arrival at the access terminal, which can be utilized for scheduling purposes. Moreover, the base station can schedule uplink transmissions for the access terminal to fulfill Quality of Service (QoS) requirements. To schedule the access terminal, feedback related to buffer information can be provided by the access terminal to the base station. In general, more up-to-date and accurate feedback can lead to the more efficient scheduling. However, a tradeoff can exist such that as more feedback is sent by the access terminal over the uplink, more uplink overhead can be utilized.
Conventionally, an access terminal can notify a base station about data arrival and buffer size using a Buffer Status Report. The Buffer Status Report can indicate an amount of data retained in a buffer associated with the access terminal to be transmitted to the base station. Moreover, a prioritized bit rate (PBR), which is an average guaranteed rate that a service will receive during reasonable radio conditions, can be fulfilled by the base station counting an amount of uplink data received for a radio bearer. As a function of this count, the base station can recognize whether the prioritized bit rate is met.
The prioritized bit rate (PBR) can be an aspect of QoS. Another aspect of QoS can be a delay bound. To fulfill the delay bound requirement, the base station can leverage knowledge of duration of elapsed time while data has been waiting in a buffer of the access terminal. Without this information, the base station can fail to prioritize access terminals optimally and efficiently while fulfilling the delay bound requirement. Currently, however, delay information it typically not transferred from access terminal to base station. Accordingly, the base station can know an amount of data in the buffer of the access terminal as provided by Buffer Status Reports, while lacking knowledge of length of time that such data has been sitting in the buffer.